Inequalities Problem..

Production Choices: The following system of inequalities models the restrictions on the number x of wooden table chairs and the number y of wooden rocking chairs made at a furniture factory each week. These restrictions are caused by limitations on the factory's equipment and labor supply

x>0
y>0
x+y<50
3x+y<90

**All the greater and less than signs are "equal" so, for the first one it's x is greater than and equal to 0. (i dont know how to do the mathematical sign)**

a) Determine each corner point of the region formed by graphing this system of inequalities.
b) The factory makes $20 for each table chair and $25 for each rocking chair. Write an expression for the priofit involving x and y
c) Evaluate the profit expression from part b at each of the corner points from part a. Which of these points produces the greates profit for the factory?